Managing Botulinum Toxin A Dosing for Laryngeal Dystonia

Laryneal dystonia (LD), also called spasmodic dysphonia, is a chronic focal dystonia that can profoundly affect communication-related quality of life. The standard of care for management of LD is repeated injection of botulinum neurotoxin (BTX) into the intrinsic laryngeal muscles. However, effects may vary based the patient and/or type of dystonia. The majority of the literature on LD focuses on the adductor subtype, which involves hyperadduction of the vocal folds, rather than abductor LD, which involves hyper abduction of the vocal folds, or the mixed subtype. Mean reported doses for adductor LD range from 1.5 to 7.5 units. The goal of this study was to evaluate presentation and treatment in a diverse group of LD patients.

A retrospective chart review of 31 adult SD patients who received at least 10 BTX injections was conducted. Demographics and primary medical history were recorded, and information on units of BTX A injected, days of breathiness post-injection, and days between injections was analyzed within LD subtypes.

Mean BTX doses were 10.2 units and 15.1 units for the adductor and abductor/mixed groups, respectively. The average dose interval was 174 days and mean post-injection breathiness interval was 21 days for the adductor group and 27 days for the abductor/mixed group.

LD patients who required high doses of BTX highlighted the differences in treatment among various LD subtypes and suggested that dose variability may occur in patients who do not respond to low-dose BTX. These results stress the importance of individualized treatment options for LD patients.